(1) Field of the Invention
The present invention relates to a process for producing directly alkylidenenorbornenes from acyclic conjugated dienes and cyclopentadienes.
(2) Description of the Prior Art
Alkylidenenorbornenes, particularly ethylidenenorbornene [5-ethylidenebicyclo (2. 2. 1) heptene-2 (hereinafter referred to simply as "EBH")] has been industrially produced as a vulcanizing termonomer for ethylene/propylene rubber.
In this connection, almost all processes for the production of EBH which have been heretofore known are those in which isomerization of vinylnorbornene 5-vinylbicyclo (2. 2. 1) heptene-2 (hereinafter referred to simply as "VBH")] is utilized. Such VBH has been produced in accordance with Diels-Alder reaction of butadiene (hereinafter referred to as "BD") and cyclopentadiene (hereinafter referred to as "CPD"). Namely, EBH has been heretofore obtained from BD and CPD according to two-stage reaction.
In this respect, it is advantageous that EBH may be produced directly from BD and CPD, in other words, EBH may be obtained in accordance with one-stage reaction operation which requires no isomerization process. That is to say, in the above-mentioned two-stage reaction, the operation of producing EBH is not only complicated but also cannot avoid the yield of EBH from being lowered due to thermo-rearrangement of VBH. Such disadvantage, however, can be overcome by using the one-stage reaction operation and therefore it is favorable process.
Processes for producing directly EBH from BD and CPD have scarcely been proposed heretofore in spite of the various advantages involved in such direct process as mentioned above. Especially, no report on such direct preparation of EBH in which a titanium-containing compound is used as the catalyst as in the present invention has been made.